This invention relates generally to reclosable end closures for containers, and more specfically to plastic end closures which seal the container for shipping and storage and which include a punch-out tab for unsealing the container, which can then be reclosed and reopened by rotation of a rotor forming part of the closure.
Plastic end closures of this reclosable type may include a one-piece stationary cap which closes the end of the container and a one-piece rotor or disc which provides various sizes and shapes of dispensing openings for dispensing the contents of the container. The one-piece cap of such closures includes a punch-out tab which seals the container during shipping and storage and which is defined by a reduced thickness tearing web. The reduced thickness tearing web is located at the bottom of a groove in the container end wall formed by the cap. The opening left by removal of the tab is substantially congruent with the largest dispensing opening in the rotor at one rotative position, to thereby establish the maximum opening for dispensing. The groove is interrupted or crossed by one or two hinge pins molded integrally with the end wall. To open the tab, downward finger pressure is manually exerted on a portion of the edge of the tab, at a point remote to the hinge pin means to thereby rupture the tearing web at that edge portion and initiate tearing (rupture) of the web. As finger pressure is maintained, the tearing of the web continues and the tab hinges inwardly from the end wall around the hinge pin means.
In such end closures, the punch-out tab is offset from the axis of rotation of the rotor or disc. The container is reclosed by rotating the rotor or disc to a position where no dispensing opening in the disc is aligned with the opening left by removal of the punch-out tab.
In one form of such end closures, the punch-out tab has been designed to be completely removable after opening, as exemplified in U.S. Pat. Nos. 2,961,132 and 3,912,128. In another form, the tab is allowed to remain hinged downwardly into the interior of the container, and need not be separately disposed of. In both such forms, the hinge pin means may break during opening, causing the tab to fall into the contents of the container. Subsequently, during dispensing of the contents of the container, the tab flows along with the other contents and tends to be dispensed therewith out through the dispensing opening. This may occur without knowledge of the user who may not see the tab and who may not be the person who originally opened the container, or who may forget the tab is in it.
In many packaging applications, the mixing of the tab with the contents of the reclosable container is nor objectionable in itself, but it is highly objectionable if there is a chance that the tab may be accidentally dispensed along with the contents intended to be dispensed.
Accidental dispensing of a punch-out tab has been positively avoided in a non-reclosable metallic container by providing an open-centered camming ring rotatably fixed to the container end wall and used to punch out a circular tab in the container end wall, as in U.S. Pat. No. 3, 877,604. In such container, the axis of the camming ring is not offset from the tab opening, as is the the axis of the rotor of a reclosable closure, but on the contrary is coaxial with the circular tab.
In such non-reclosable container, the open center of the camming ring is of a smaller diameter than the circular tab, and covers the edge of the tab so that manual pressure directly at the edge cannot be exerted. Covering of the edge of the tab, or of the edge of the opening left by the tab, is necessary to establish the desired interference fit. However, downward compressive pressure on the edge of the tab is still relied on, even though the edge is covered, such downward compressive pressure being provided by a camming action between the overlying coaxial ring and cam surfaces formed in the tab at the edge of the tab.
Such a container cannot be made reclosable by a rotor or disc with an axis of rotation offset from the opening left by the tab, because the coaxial camming ring interferes. I have determined however that rupturing of the covered edge of a punch-out tab in plastic end closures, of conventional composition such as polystyrene, can be satisfactorily accomplished without the imposition of downward compressive pressure at a covered tab edge, and by reliance instead on indirect application of tensile pressure to the edge through manual compressive pressure on the exposed parts of the tab radially inward of the covered edge.
The present invention provides for applying tab-edge rupturing forces in this manner, and for the first time accomplishes positive prevention of accidental dispensing of a punch-out tab in a plastic end closure of the reclosable kind. The interference fit which prevents accidental dispensing of the tab forces reliance on indirect application of tensile pressure to rupture the tab edge, but near congruency between at least a portion of the tab-edge and a portion of the largest opening in the rotor is sufficient to allow this indirect application of tensile pressure to be effective.